U.S. patent application number 14/566674 was filed with the patent office on 2016-06-16 for sensing and storage system for fluid balance.
This patent application is currently assigned to Medtronic, Inc.. The applicant listed for this patent is Medtronic,Inc.. Invention is credited to William P. Hajko, Thomas P. Hartranft, Thomas E. Meyer.
Application Number | 20160166748 14/566674 |
Document ID | / |
Family ID | 54477967 |
Filed Date | 2016-06-16 |
United States Patent
Application |
20160166748 |
Kind Code |
A1 |
Meyer; Thomas E. ; et
al. |
June 16, 2016 |
SENSING AND STORAGE SYSTEM FOR FLUID BALANCE
Abstract
A sensing and storage system for fluid balance during dialysis
is provided. The sensing and storage system has flow sensors on
either side of a dialyzer in a controlled volume dialysate flow
path. The sensors are positioned so that no fluid can be added to
or removed from the dialysate flow path between the sensors except
for that which is added or removed by action of a control pump. The
sensing and storage system can have a fluid removal line for the
removal of fluid from the dialysate flow loop.
Inventors: |
Meyer; Thomas E.;
(Stillwater, MN) ; Hajko; William P.; (Safety
Harbor, FL) ; Hartranft; Thomas P.; (Clearwater,
FL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Medtronic,Inc. |
Minneapolis |
MN |
US |
|
|
Assignee: |
Medtronic, Inc.
Minneapolis
MN
|
Family ID: |
54477967 |
Appl. No.: |
14/566674 |
Filed: |
December 10, 2014 |
Current U.S.
Class: |
210/646 ;
210/137 |
Current CPC
Class: |
A61M 1/1696 20130101;
A61M 2205/3365 20130101; A61M 1/1601 20140204; A61M 1/1647
20140204; A61M 2205/3334 20130101 |
International
Class: |
A61M 1/16 20060101
A61M001/16 |
Claims
1. A sensing and storage system for fluid balance during dialysis,
comprising; a control pump in a dialysate flow loop in fluid
communication with a dialyzer, wherein the dialysate flow loop has
a controlled volume; a fluid removal line fluidly connected to the
dialysate flow loop and in communication with the control pump; an
extracorporeal flow loop in fluid communication with the dialysate
flow loop across a semi-permeable membrane in the dialyzer; an
inflow sensor in the dialysate flow loop and positioned in the
dialysate flow loop at a position before the dialyzer; an outflow
sensor in the dialysate flow loop and positioned in the dialysate
flow loop at a position after the dialyzer; and wherein the outflow
sensor and the inflow sensor are in electronic communication with
the control pump.
2. The sensing and storage system of claim 1 wherein the dialysate
flow loop is controlled compliant dialysis.
3. The sensing and storage system of claim 1, further comprising at
least one fluid pump other than the control pump fluidly connected
to a fluid source and in fluid communication with the dialysate
flow loop; wherein the at least one fluid pump other than the
control pump is positioned in the dialysate flow loop at a position
after the outflow sensor and before the inflow sensor.
4. The sensing and storage system of claim 3 wherein the
extracorporeal flow loop has at least one blood pump.
5. The sensing and storage system of claim 3 wherein the at least
one fluid pump other than the control pump is selected from the
group consisting of a sodium chloride pump in fluid communication
with a sodium chloride reservoir, a water pump in fluid
communication with a water reservoir, a cation infusate pump in
fluid communication with a cation infusate reservoir, a bicarbonate
pump in fluid communication with a bicarbonate reservoir, and
combinations thereof.
6. The sensing and storage system of claim 1 wherein a fluid
removal prescription is set for a patient, and the pump rate of the
control pump is automatically adjusted to remove a prescribed
amount of fluid based on the inputs from the inflow sensor and the
outflow sensor, wherein the adjustment of the pump rate of the
control pump is determined by a deviation of the fluid removal
prescription from a difference between the flow rate of dialysate
at the inflow sensor and the flow rate of dialysate at the outflow
sensor.
7. The sensing and storage system of claim 1 wherein the control
pump is a peristaltic pump.
8. The sensing and storage system of claim 1 wherein the control
pump is capable of moving fluid bi-directionally.
9. The sensing and storage system of claim 1, further comprising a
control reservoir fluidly connected to the fluid removal line.
10. The sensing and storage system of claim 9 wherein the control
reservoir has a fluid capacity of between 1 L and 30 L, between 1 L
and 3 L, between 3 L and 10 L, between 8 L and 15 L, between 12 L
and 20 L, between 15 and 18 L, or between 18 L and 30 L.
11. The sensing and storage system of claim 9 wherein the control
reservoir is fluidly connected to a drain, and further comprising a
clamp on the control reservoir to control the movement of fluid
from the control reservoir to the drain.
12. The sensing and storage system of claim 1, wherein one or more
additional flow sensors are provided between any fluid pump and a
dialyzer inlet.
13. The sensing and storage system of claim 2, further comprising
one or more additional flow sensor positioned between a dialyzer
outlet and the at least one fluid pump other than the control
pump.
14. A method of controlling fluid removed from a patient during
dialysis, comprising the steps of: obtaining a fluid removal
prescription for a patient; determining the rate of fluid flow in a
dialysate flow loop on an inlet side of a dialyzer, wherein the
dialysate flow loop has a controlled volume; determining the rate
of fluid flow in the dialysate flow loop on an outlet side of the
dialyzer; determining the deviation of the fluid removal
prescription from the difference in the flow rate on the inlet side
of the dialyzer and the flow rate on the outlet side of the
dialyzer; and adjusting the pump rate of a control pump based on
the deviation wherein the control pump is capable of moving fluid
from a dialysate flow loop into a fluid removal line.
15. The method of claim 14 further comprising adding fluid to the
dialysate flow path from any one or more of a control reservoir, a
water reservoir, a sodium chloride reservoir, an infusate
reservoir, or a bicarbonate reservoir; wherein the fluid is added
at a position in the dialysate flow path located before the inflow
sensor and after the outflow sensor.
16. The method of claim 14 further comprising a control system,
wherein the control system automatically adjusts the pump rate of
the control pump based on the deviation wherein the control pump is
capable of moving fluid from the dialysate flow loop into the fluid
removal line.
17. The method of claim 14, further comprising transferring fluid
from the dialysate flow path to an extracorporeal circuit to
deliver a fluid bolus to a patient.
18. The method of claim 14, further comprising transferring a
volume of fluid from the dialysate flow path to an extracorporeal
flow path, wherein transferring the volume of fluid to the
extracorporeal flow path results in blood in the extracorporeal
flow path being returned to a patient.
19. The method of claim 14, wherein the rate of fluid flow in the
dialysate flow loop on the inlet side of the dialyzer is determined
with an inflow sensor, and the rate of fluid flow in the dialysate
flow loop on the outlet side of the dialyzer is determined with an
outflow sensor.
20. The method of claim 15, wherein fluid is added to the dialysate
flow path from the water reservoir, the sodium chloride reservoir,
the infusate reservoir, or the bicarbonate reservoir with the use
of one or more fluid pumps.
21. The method of claim 20, further comprising stopping the one or
more fluid pumps, determining the rate of flow in the dialysate
flow loop on the inlet side of the dialyzer with an inflow sensor,
determining the rate of flow in the dialysate flow loop on the
outlet side of the dialyzer with an outflow sensor, comparing the
rate of flow on the inlet side of the dialyzer to the rate of flow
on the outlet side of the dialyzer; and determining whether
difference between the rate of flow is within a predetermined
limit.
Description
FIELD OF THE INVENTION
[0001] The invention relates to a system for sensing and storing
fluids during dialysis. The system allows for balancing fluid
levels during therapy.
BACKGROUND
[0002] Kidney dialysis is a medical procedure that is performed to
aid or replace some of the kidney functions in severe renal
failure. Hemodialysis, hemofiltration, hemodiafiltration, and
peritoneal dialysis are all replacement therapies for patients who
have lost most or all of their kidney function. Dialysis can remove
many of the toxins and wastes that the natural kidney would remove
in healthy patients. In addition, these therapies are used to
balance the electrolyte or blood salt levels and to remove excess
fluid that accumulates in patients with renal failure.
[0003] In addition to removing toxins and wastes from patients with
kidney disease, excess fluid accumulated in patients suffering from
renal failure is generally removed by the ultrafiltration action of
a dialysis procedure. Removing fluid too slowly from a patient
renders the fluid removal therapy inefficient, and may force the
patient to undergo a longer procedure than necessary to remove the
correct amount of fluid. If the treatment is ended with
insufficient fluid removal, the patient can suffer from
cardiovascular and pulmonary complications related to the resultant
hypervolemia. Removing too much fluid from a patient, or removing
fluid too quickly from a patient, can cause a dangerous loss of
blood pressure.
[0004] Some methods for controlling the amount of fluid removed
from a patient are known in the art. U.S. Ser. No. 13/864,913
describes a system using two tubes connected to a pump, wherein one
tube delivers fresh dialysate into the system and removes fluid
from a control bag into a drain, and the second tube removes fluid
into a control bag. The change in weight in the control bag is
therefore due to the net ultrafiltrate removed from the
patient.
[0005] U.S. Pat. No. 8,202,241B2 teaches a blood purification
system comprising multiple scales. A scale is provided for each
storage container in the system. The net amount of fluid removed
from a patient is therefore the sum of all of the changes in weight
from each of the scales. The pump rates of the pumps attached to
each of the storage containers can be changed if the net rate of
fluid removed from the patient varies from some pre-set rate.
[0006] US20120085707A1 teaches a blood removal system with two
pumps; one on either side of a dialyzer, and a dialysate reservoir
on a scale. The two pumps are in communication with a control
system. The output pump drives fluid from the dialyzer into a
dialysate reservoir, while the input pump drives fluid from the
dialysate reservoir to the dialyzer. The net amount of fluid
removed from the patient is proportional to the change in the
weight of the dialysate reservoir. If the change in the weight of
the dialysate reservoir does not match the fluid removal
prescription, then the pump rate of the output pump can be
increased, or the pump rate of the input pump can be decreased.
[0007] The known dialysis systems outlined above balance fluid
levels during therapy through gravimetric control, determining the
net amount of fluid added or removed to the dialysate by the
changes in the weights of various containers. These additional
scales or control systems add to the size, weight and cost of the
dialysis system. Other known methods for fluid balancing involve
the use of coordination of the pumps that add fluid to the system
and the pumps that remove fluid from the system. This requires
highly accurate pumping means for each pump. These additional
control systems necessarily add to the size, weight and cost of the
dialysis system, and the highly accurate pumps add to the total
cost of the dialysis system.
[0008] Some known systems control fluid movement across the
dialysis membrane by means of balance chambers that coordinately
pump equal volumes of fluid into and out of the dialysate ports of
the dialyzer. The balance chambers comprise a fixed volume
partitioned by a membrane or piston and, as fluid enters on one
side of the partition, the partition is displaced by the incoming
fluid and an equal amount of fluid is expelled on the other side of
the partition. In balance chamber systems, net fluid removal from
the patient across the dialysis membrane is accomplished by adding
a fluid removal pump in fluid communication with the dialyzer
outflow port and the outflow side of the of the balance chamber
partition. In such systems operation of the fluid removal pump
causes a greater amount of fluid to pass out of the dialyzer than
into the dialyzer, resulting in net fluid removal from the patient
across the dialysis membrane. In balance chamber systems the
accuracy of patient fluid removal is dependent upon the accuracy of
the fluid removal pump and other factors that can degrade the
volumetric accuracy of the balance chambers such as fluid leaks
within the balance chamber system and gas bubbles in the dialysate.
Balance chambers can result in a pulsatile flow and if a smooth
flow is desired, multiple sets of balance chambers are employed to
reduce the pulsatility. Balance chambers can also increase the size
and weight of a hemodialysis system as well as the total fluid
volume required to operate the dialysate circuit and can be
undesirable for hemodialysis systems that are small, portable and
operate with a reduced amount of water.
[0009] Hence, there is a need for a system that can sense and
balance the fluid levels during renal therapy. There is a need for
a system that can selectively and accurately control the amount of
fluid added to or removed from the patient during dialysis to
ensure effective treatment and patient safety, without additional
equipment that can add to the size and cost of the therapy
system.
SUMMARY OF THE INVENTION
[0010] The first aspect of the invention is drawn to a storage and
sensing system for fluid balance during dialysis. In any embodiment
of the first aspect of the invention, the storage and sensing
system can comprise a control pump in a dialysate flow loop in
fluid communication with a dialyzer, wherein the dialysis flow loop
has a controlled volume; a fluid removal line fluidly connected to
the dialysate flow loop and in communication with the control pump;
an extracorporeal flow loop in fluid communication with the
dialysate flow loop across a semi-permeable membrane in the
dialyzer; an inflow sensor in the dialysate flow loop positioned in
the dialysate flow loop at a position before the dialyzer; and an
outflow sensor in the dialysate flow loop and positioned in the
dialysate flow loop at a position after the dialyzer; the outflow
sensor and the inflow sensor can be in electronic communication
with the control pump.
[0011] In any embodiment of the first aspect of the invention, the
sensing and storage system can be part of a controlled compliant
dialysis system. In any embodiment of the first aspect of the
invention, the dialysate flow loop is controlled compliant.
[0012] In any embodiment of the first aspect of the invention, the
sensing and storage system can comprise at least one fluid pump
other than the control pump fluidly connected to a fluid source and
in fluid communication with the dialysate flow loop; wherein the at
least one fluid pump other than the control pump is positioned in
the dialysate flow loop at a position after the outflow sensor and
before the inflow sensor.
[0013] In any embodiment of the first aspect of the invention, the
extracorporeal flow loop can have at least one blood pump.
[0014] In any embodiment of the first aspect of the invention, the
sensing and storage system can comprise more than one pump other
than the control pump.
[0015] In any embodiment of the first aspect of the invention, the
at least one fluid pump other than the control pump can be selected
from the group comprising a sodium chloride pump in fluid
communication with a sodium chloride reservoir, a water pump in
fluid communication with a water reservoir, a cation infusate pump
in fluid communication with a cation infusate reservoir, a
bicarbonate pump in fluid communication with a bicarbonate
reservoir, and combinations thereof.
[0016] In any embodiment of the first aspect of the invention, a
fluid removal prescription can be set for a patient, and the pump
rate of the control pump can be automatically adjusted to remove a
prescribed amount of fluid based on the inputs from the inflow
sensor and the outflow sensor, wherein the adjustment of the pump
rate of the control pump is determined by a deviation of the fluid
removal prescription from a difference between the flow rate of
dialysate at the inflow sensor and the flow rate of the dialysate
at the outflow sensor.
[0017] In any embodiment of the first aspect of the invention, the
control pump can be a peristaltic pump. In any embodiment of the
first aspect of the invention, the control pump can be capable of
moving fluid bi-directionally.
[0018] In any embodiment of the first aspect of the invention, a
control reservoir can be fluidly connected to the fluid removal
line.
[0019] In any embodiment of the first aspect of the invention, the
fluid removal line can be in fluid communication with a plumbing
drain or waste line.
[0020] In any embodiment of the first aspect of the invention, the
control reservoir can have a fluid capacity of between 1 L and 30
L, between 1 L and 3 L, between 3 L and 10 L, between 8 L and 15 L,
between 12 L and 20 L, between 15 and 18 L, or between 18 L and
30.
[0021] In any embodiment of the first aspect of the invention, the
control reservoir can be fluidly connected to a drain, and the
system can comprise a clamp on the control reservoir to control the
movement of fluid from the control reservoir to the drain.
[0022] In any embodiment of the first aspect of the invention, one
or more additional flow sensors can be provided between any fluid
pump and the dialyzer inlet. In any embodiment of the first aspect
of the invention, one or more additional flow sensors can be
provided between the dialyzer outlet and the at least one pump
other than the control pump.
[0023] Any of the features described as being part of the first
aspect of the invention can be included in the first aspect of the
invention alone or in combination.
[0024] The second aspect of the invention is drawn to a method of
controlling fluid removed from a patient during dialysis. In any
embodiment of the second aspect of the invention, the method can
comprise obtaining a fluid removal prescription for a patient,
determining the rate of fluid flow in a dialysate flow loop on an
inlet side of a dialyzer, wherein the dialysate flow loop has a
controlled volume, determining the rate of fluid flow in the
dialysate flow loop on an outlet side of the dialyzer, determining
the deviation of the fluid removal prescription from the difference
in the flow rate on the inlet side of the dialyzer and the flow
rate on the outlet side of the dialyzer, and adjusting the pump
rate of a control pump based on the deviation wherein the control
pump is capable of moving fluid from a dialysate flow loop into a
fluid removal line.
[0025] In any embodiment of the second aspect of the invention, the
fluid removal line can be fluidly connected to a control reservoir.
In any embodiment of the second aspect of the invention, the
control reservoir can be replaced with a drain line in fluid
communication with a control pump.
[0026] In any embodiment of the second aspect of the invention, one
or more additional inflow sensors and/or one or more additional
outflow sensors can be provided as part of an independent
protective system to protect against failures in the primary
control system for patient net fluid removal.
[0027] In any embodiment of the second aspect of the invention, the
method can comprise removing or adding fluid to the dialysate flow
path from any one or more of a control reservoir, a water
reservoir, a sodium chloride reservoir, an infusate reservoir, or a
bicarbonate reservoir; wherein the fluid is removed or added at a
position located in the dialysate flow path located before the
inflow sensor and after the outflow sensor.
[0028] In any embodiment of the second aspect of the invention, the
system can further comprise a control system and the control system
can automatically adjust the pump rate of the control pump based on
the deviation, wherein the control pump is capable of moving fluid
from the dialysate flow loop into the fluid removal line.
[0029] In any embodiment of the second aspect of the invention, the
method can further comprise transferring fluid from the dialysate
flow path to an extracorporeal circuit to deliver a fluid bolus to
a patient.
[0030] In any embodiment of the second aspect of the invention, the
method can further comprise transferring a volume of fluid from the
dialysate flow path to an extracorporeal flow path, wherein
transferring the volume of fluid to the extracorporeal flow path
results in blood in the extracorporeal flow path being returned to
a patient.
[0031] In any embodiment of the second aspect of the invention, the
rate of fluid flow in the dialysate flow loop on the inlet side of
the dialyzer can be determined with an inflow sensor, and the rate
of fluid flow in the dialysate flow loop on the outlet side of the
dialyzer can be determined with an outflow sensor.
[0032] In any embodiment of the second aspect of the invention, the
fluid can be added to the dialysate flow path from the control
reservoir, the water reservoir, the sodium chloride reservoir, the
infusate reservoir, or the bicarbonate reservoir with the use of
one or more fluid pumps.
[0033] In any embodiment of the second aspect of the invention, the
method can comprise stopping the one or more fluid pumps,
determining the rate of flow in the dialysate flow loop on the
inlet side of the dialyzer with an inflow sensor, determining the
rate of flow in the dialysate flow loop on the outlet side of the
dialyzer with an outflow sensor, comparing the rate of flow on the
inlet side of the dialyzer to the rate of flow on the outlet side
of the dialyzer; and determining whether difference between the
rate of flow is within a predetermined limit.
[0034] Any of the features described as being part of the second
aspect of the invention can be included in the second aspect of the
invention, either alone or in combination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0035] FIG. 1 shows a schematic of a dialysis system utilizing the
sensing and storage system of the present invention.
[0036] FIG. 2 is a flow diagram showing the operation of the fluid
sensing and storage system.
DETAILED DESCRIPTION OF THE INVENTION
[0037] Unless defined otherwise, all technical and scientific terms
used herein generally have the same meaning as commonly understood
by one of ordinary skill in the relevant art.
[0038] The articles "a" and "an" are used herein to refer to one or
to more than one (i.e., to at least one) of the grammatical object
of the article. By way of example, "an element" means one element
or more than one element.
[0039] The term "before," as used when referring to relative
positions of components of a dialysis system, refers to an upstream
position in the normal operational flow direction of the dialysis
system. The term "after" refers to a downstream position in the
normal operational flow direction of the dialysis system.
[0040] The term "bicarbonate reservoir" refers to a container that
can be a stand-alone container or alternatively can be integrally
formed with an apparatus for hemodialysis, hemodiafiltration, or
hemofiltration. The bicarbonate reservoir can store a source of
buffering material, such as sodium bicarbonate, and can be
configured to interface with at least one other functional module
found in systems for hemodialysis, hemodiafiltration, or
hemofiltration. For example, the bicarbonate reservoir can contain
at least one fluid pathway and include components such as conduits,
valves, filters or fluid connection ports. The bicarbonate
reservoir can be disposable or be consumable wherein the reservoir
is recharged upon depletion. Specifically, the term "bicarbonate
consumables container" refers to an object or apparatus having or
holding a material in solid and/or solution form that is a source
of bicarbonate, such as sodium bicarbonate, that is depleted during
operation of the system. The object or apparatus may be single use,
or may be replenished and used multiple times, for example, by
refilling the object to replace the consumed material.
[0041] The term "blood pump" refers to a device to move or convey
fluid through an extracorporeal circuit. The pump may be of any
type suitable for pumping blood, including those known to persons
of skill in the art, for example peristaltic pumps, tubing pumps,
diaphragm pumps, centrifugal pumps, and shuttle pumps.
[0042] A "bolus" or "fluid bolus" is a volume of fluid. The bolus
or fluid bolus can optionally be delivered to the blood of the
patient.
[0043] "Bypass line" refers to a line, connected to the main line,
through which fluid or gas may alternatively flow.
[0044] The term "cartridge" refers to any container designed to
contain a powder, fluid, or gas made for ready connection to a
device or mechanism. The container can have one or more
compartments. Instead of compartments, the container can also be
comprised of a system of two or more modules connected together to
form the cartridge wherein the two or more modules once formed can
be connected to a device or mechanism.
[0045] The term "cation infusate reservoir" refers to a source from
which cations can be obtained. Examples of cations include, but are
not limited to, calcium, magnesium and potassium. The source can be
a solution containing cations or a dry composition that is hydrated
by the system. The cation infusate reservoir is not limited to
cations and may optionally include other substances to be infused
into a dialysate or replacement fluid; non-limiting examples can
include glucose, dextrose, acetic acid and citric acid.
[0046] The terms "communicate" and "communication" include, but are
not limited to, the connection of system electrical elements,
either directly or remotely, for data transmission among and
between said elements. The terms also include, but are not limited
to, the connection of system fluid elements enabling fluid
interface among and between said elements.
[0047] The term "comprising" includes, but is not limited to,
whatever follows the word "comprising." Thus, use of the term
indicates that the listed elements are required or mandatory but
that other elements are optional and may or may not be present.
[0048] The term "connectable" refers to being able to be joined
together for purposes including, but not limited to, maintaining a
position, allowing a flow of fluid, performing a measurement,
transmitting power, and transmitting electrical signals. The term
"connectable" can refer to being able to be joined together
temporarily or permanently.
[0049] A "connector" and "for connection" as used herein describe
the concept of forming a fluid connection between two components
wherein fluid or gas can flow from one component, through a
connector or a component for connection, to another component. The
connector provides for a fluid connection in its broadest sense and
can include any type of tubing, fluid or gas passageway, or conduit
between any one or more components of the invention.
[0050] The term "consisting of" includes and is limited to whatever
follows the phrase "consisting of." Thus, the phrase indicates that
the limited elements are required or mandatory and that no other
elements may be present. The term "consisting essentially of"
includes whatever follows the term "consisting essentially of" and
additional elements, structures, acts or features that do not
affect the basic operation of the apparatus, structure or method
described.
[0051] The term "container" as used herein in the context of a
controlled volume circuit or flow path is a receptacle that may be
flexible or inflexible for holding any fluid or solid, such as for
example a spent dialysate fluid, or a sodium chloride or sodium
bicarbonate solution or solid, or the like.
[0052] The terms "controlled compliance" and "controlled compliant"
describe the ability to actively control the transfer of fluid
volume into or out of a compartment, flow path or circuit. In any
embodiment, the variable volume of fluid in a dialysate circuit or
controlled compliant flow path expands and contracts via the
control of one or more pumps in conjunction with one or more
reservoirs. The volume of fluid in the system is generally constant
(unless additional fluids are added to a reservoir from outside of
the system) once the system is in operation if patient fluid
volume(s), flow paths, and reservoirs are considered part of the
total volume of the system (each individual volume may sometimes be
referred to as a fluid compartment). The attached reservoirs allow
the system to adjust the patient fluid volume by withdrawing fluid
and storing the desired amount in an attached control reservoir
and/or by providing purified and/or rebalanced fluids to the
patient and optionally removing waste products. The terms
"controlled compliance" and "controlled compliant" are not to be
confused with the term "non-compliant volume," which simply refers
to a vessel, conduit, container, flow path, conditioning flow path
or cartridge that resists the introduction of a volume of fluid
after air has been removed from a defined space such as a vessel,
conduit, container, flow path, conditioning flow path or cartridge.
In any embodiment, the controlled compliant system can move fluids
bi-directionally. In certain cases, the bi-directional fluid
movement can be across a semi-permeable membrane either inside or
outside a dialyzer. The bi-directional fluid flow can also occur
across, through, or between vessels, conduits, containers, flow
paths, conditioning flow paths or cartridges of the invention in
selected modes of operation. The term "moving fluid
bi-directionally" as used in connection with a barrier, such as a
semi-permeable membrane, refers to the ability to move fluid across
the barrier in either direction. "Moving fluid
bi-directionally"also can apply to the ability to move fluid in
both directions in the flow path or between a flow path and
reservoir in a controlled compliant system.
[0053] The terms "controlled compliant flow path," "controlled
compliant dialysate flow path" and "controlled compliant solution
flow path" refer to flow paths operating within a controlled
compliant system having the characteristic of controlled
compliance, or of being controlled compliant as defined herein.
[0054] The term "controlled volume" refers to a flow path or system
wherein a volume of fluid in the flow path or system, exclusive of
any volume of fluid contained in an external reservoir, supply
line, or fluid removal line, is substantially fixed. In any
embodiment, a controlled volume flow path is not fluidly connected
to, nor includes, an open reservoir or a reservoir having a
variable volume, such as a reservoir made of a flexible
material.
[0055] A "control pump" is a means capable of moving fluid through
a system at a specific rate. The term "control pump" can include
for example an "ultrafiltrate pump," which is a pump that is
operable to pump fluid bi-directionally to actively control the
transfer of fluid volume into or out of a compartment or
circuit.
[0056] A "control reservoir" is a container capable of containing
fluid that has been removed from a dialysate flow path or fluid to
be added to a dialysate flow path.
[0057] A "control system" consists of combinations of components
that act together to maintain a system to a desired set of
performance specifications. The control system can use processors,
memory and computer components configured to interoperate to
maintain the desired performance specifications. The control system
can also include fluid or gas control components, and solute
control components as known within the art to maintain the
performance specifications.
[0058] To "deliver a fluid bolus to a patient" means to control a
dialysis system so that a volume of fluid can be delivered to a
patient. Optionally, the volume of fluid can be transferred across
a membrane via a dialyzer and into an extracorporeal flow path for
delivery to the patient.
[0059] The term "deviation of the fluid removal prescription"
refers to any difference between a fluid removal rate or volume set
in a fluid removal prescription from the actual rate or volume of
fluid removed during a dialysis session.
[0060] "Dialysate" is the fluid that passes through the dialyzer on
the side of the dialysis membrane that is opposite to the fluid
(e.g. blood) that is being dialyzed.
[0061] The term "dialysate flow loop," "dialysate flow path" or
"dialysate conduit flow path" refers to any portion of a fluid
pathway that conveys a dialysate and is configured to form at least
part of a fluid circuit for hemodialysis, hemofiltration,
hemodiafiltration or ultrafiltration.
[0062] "Dialysis" is a type of filtration, or a process of
selective diffusion through a membrane. Dialysis removes solutes of
a specific range of molecular weights via diffusion through a
membrane from a fluid to be dialyzed into a dialysate. During
dialysis, a fluid to be dialyzed is passed over a filter membrane,
while dialysate is passed over the other side of that membrane.
Dissolved solutes are transported across the filter membrane by
diffusion between the fluids. The dialysate is used to remove
solutes from the fluid to be dialyzed. The dialysate can also
provide enrichment to the other fluid.
[0063] The terms "dialysis membrane," "hemodialysis membrane,"
"hemofiltration membrane," "hemodiafiltration membrane" and
"ultrafiltration membrane" can generally be referred to as a
"membrane," or can refer to a semi-permeable barrier selective to
allow diffusion and/or convection of solutes between blood and
dialysate, or blood and filtrate, of a specific range of molecular
weights in either direction through the barrier that separates
blood and dialysate, or blood and filtrate, while allowing
diffusive and/or convective transfer between the blood on one side
of the membrane and the dialysate or filtrate circuit on the other
side of the membrane.
[0064] The term "dialyzer" refers to a cartridge or container with
two flow paths separated by semi-permeable membranes. One flow path
is for blood and one flow path is for dialysate. The membranes can
be in the form of hollow fibers, flat sheets, or spiral wound or
other conventional forms known to those of skill in the art.
Membranes can be selected from the following materials of
polysulfone, polyethersulfone, poly(methyl methacrylate), modified
cellulose, or other materials known to those skilled in the
art.
[0065] The term "dialyzer inlet" refers to a fluid pathway in a
dialyzer configured to allow fluid to enter the dialyzer through a
fluid pathway.
[0066] The term "dialyzer outlet" refers to a fluid pathway in a
dialyzer configured to allow fluid to exit the dialyzer through a
fluid pathway.
[0067] A "drain" is any external fluid line designed to transport
fluid that has been removed from the system and is not to be
returned to the system.
[0068] "Electronic communication" refers to the connection between
the electrical elements of the system, either directly or
wirelessly.
[0069] The term "extracorporeal," as used herein generally means
situated or occurring outside the body.
[0070] The term "extracorporeal circuit" or "extracorporeal flow
loop" refers to a fluid pathway incorporating one or more
components such as but not limited to conduits, valves, pumps,
fluid connection ports or sensing devices configured therein such
that the pathway conveys blood from a subject to an apparatus for
hemodialysis, hemofiltration, hemodiafiltration or ultrafiltration
and back to the subject.
[0071] "Flow" refers to the movement of a fluid or gas.
[0072] The term "flow loop" refers to a grouping of components that
may guide the movement of a fluid, convey the fluid, exchange
energy with the fluid, modify the composition of the fluid, measure
a characteristic of the fluid and/or detect the fluid. A flow loop
comprises a route or a collection of routes for a fluid to move
within. Within a flow loop there may be more than one route that a
volume of fluid can follow to move from one position to another
position. A fluid volume may move through a flow loop such that the
fluid volume recirculates, or passes the same position more than
once as the fluid volume moves through a flow loop. A flow loop may
operate to cause fluid volume ingress to and fluid volume egress
from the flow loop. The term "flow loop" and "flow path" often may
be used interchangeably.
[0073] A "fluid" is a subset of the phases of matter and can
include liquids, gases, plasmas and, to some extent, plastic
solids. Notably, a liquid, as used herein, can therefore also have
a mixture of gas and liquid phases of matter.
[0074] The term "fluid balance" refers a fluid state in which the
amount of fluid leaving a compartment (e.g. the body during
dialysis) is equal to the fluid entering the compartment. In
general, "fluid balance" can also refer to the maintenance of the
overall balance of fluid added to a compartment and the fluid
withdrawn from the compartment.
[0075] The term "fluid communication" refers to the ability of
fluid or gas to move from one component or compartment to another
within a system or the state of being connected, such that fluid or
gas can move by pressure differences from one portion that is
connected to another portion.
[0076] The terms "fluidly connectable" and "fluid connection" refer
to the ability of providing for the passage of fluid or gas from
one point to another point. The two points can be within or between
any one or more of compartments, modules, systems, components, and
rechargers, all of any type.
[0077] A "fluid pump," as used herein, refers to a pump capable of
moving a fluid through a flow path.
[0078] A "fluid removal line" is a fluid pathway or fluid line for
removing fluid, gas, or mixtures thereof from a fluid pathway or a
fluid line during any one of hemodialysis, hemofiltration,
hemodiafiltration, ultrafiltration, or peritoneal dialysis. The
fluid removal line can also optionally be used to remove fluid
during a cleaning or priming cycle as required. The "fluid removal
line" can also introduce fluid back into a fluid pathway from which
the "fluid removal line" generally operates to remove fluid
depending on a required operation or desired function
[0079] A "fluid removal prescription" refers to the net amount of
fluid that is intended to be removed from a patient during a
dialysis session.
[0080] "Infusate" is a solution of one or more salts for the
adjustment of the composition of a dialysate.
[0081] An "inflow sensor" is a sensor that can measure the rate of
flow of a fluid at a position at or before the inlet of the
dialyzer.
[0082] An "inlet side of a dialyzer" refers to the side of a
dialyzer comprising a fluid inlet.
[0083] An "operational line" or "line" is a passageway, conduit or
connector that directs fluid or gas in a path used while the system
is in operation.
[0084] An "outflow sensor" is a sensor that can measure the rate of
flow of a fluid at a position at or after the outlet of the
dialyzer.
[0085] An "outlet side of a dialyzer" refers to the side of a
dialyzer comprising a fluid outlet.
[0086] The terms "pathway," "conveyance pathway," "fluid flow
path," and "flow path" refer to the route through which a fluid or
gas, such as dialysate or blood, travels.
[0087] A "patient" or "subject" is a member of any animal species,
preferably a mammalian species, optionally a human. The subject can
be an apparently healthy individual, an individual suffering from a
disease, or an individual being treated for a disease.
[0088] The term "peristaltic pump" refers to a pump that operates
by compression of a flexible conduit or tube through which the
fluid to be pumped passes.
[0089] The term "physiologically compatible fluid" or
"physiologically compatible solution" refers to a fluid that can be
safely introduced into the bloodstream of a living subject.
[0090] A "predetermined limit" refers to one or more variables that
are set to a defined number or range of numbers in advance.
[0091] The term "pump" refers to any device that causes the
movement of fluids or gases by the application of suction or
pressure.
[0092] The terms "pump rate" and "volumetric pumping rate" refer to
the volume of fluid that a pump conveys per unit of time.
[0093] A "sensor" is a component capable of determining the states
of one or more variables in a system.
[0094] The terms "sodium chloride reservoir" and "sodium chloride
container" refer to an object that can be a stand-alone enclosure
or alternatively can be integrally formed with an apparatus for
hemodialysis, hemodiafiltration, or hemofiltration. The object can
store a source of sodium, such as sodium chloride in solid and/or
solution form, and can be configured to interface with at least one
other functional module found in systems for hemodialysis,
hemodiafiltration, or hemofiltration. For example, the sodium
chloride reservoir or container can contain at least one fluid
pathway and include components such as conduits, valves, filters or
fluid connection ports.
[0095] "Sorbent cartridge" refers to a cartridge that can contain
one or more sorbent materials. The cartridge can be connected to a
dialysis flow path. The sorbent materials in the sorbent cartridge
are used for removing specific solutes from solution, such as urea.
The sorbent cartridge can have a single compartmental design
wherein all sorbent materials necessary for performing dialysis are
contained within the single compartment. Alternatively, the sorbent
cartridge can have a modular design wherein the sorbent materials
are dispersed across at least two different modules, which can be
connected to form a unitary body. Once the at least two modules are
connected together, the connected modules can be referred to as a
sorbent cartridge, which can be fitted to a device or mechanism.
When a single module contains all the sorbent materials necessary
for performing dialysis, the single module can be referred to as a
sorbent cartridge.
[0096] "Spent dialysate" is a dialysate contacted with blood
through a dialysis membrane and contains one or more impurity, or
waste species, or waste substance, such as urea.
[0097] The term "substantially inflexible volume" refers to a
three-dimensional space within a vessel or container that can
accommodate a maximum amount of non-compressible fluid and resists
the addition of any volume of fluid above the maximum amount. The
presence of a volume of fluid less than the maximum amount will
fail to completely fill the vessel or container. Once a
substantially inflexible volume has been filled with a fluid,
removal of fluid from that volume will create a negative pressure
that resists fluid removal unless fluid is added and removed
simultaneously at substantially equal rates. Those skilled in the
art will recognize that a minimal amount of expansion or
contraction of the vessel or container can occur in a substantially
inflexible volume; however, addition or subtraction of a
significant volume of fluid over the maximum or minimum will be
resisted.
[0098] The term "ultrafiltrate" refers to fluid that is removed
from a subject by convection through a permeable membrane during
hemodialysis, hemofiltration, hemodiafiltration, or peritoneal
dialysis. The term "ultrafiltrate," as used herein, can also refer
to the fluid in a reservoir that collects fluid volume removed from
the patient, but such a reservoir may also include fluids or
collections of fluids that do not originate from the subject.
[0099] An "ultrafiltrate reservoir" is a container for storing
fluid removed from a subject during hemodialysis, hemofiltration,
hemodiafiltration or peritoneal dialysis.
[0100] The term "ultrafiltration" refers to subjecting a fluid to
filtration, where the filtered material is very small; typically,
the fluid comprises colloidal, dissolved solutes or very fine solid
materials, and the filter is a microporous, nanoporous, or
semi-permeable medium. A typical medium is a membrane. During
ultrafiltration, a "filtrate" or "ultrafiltrate" that passes
through the filter medium is separated from a feed fluid. In
certain instances, the use of the term "filtrate" can refer to the
fluid generated during hemofiltration. In general, when transport
across a membrane is predominantly diffusive as a result of a
concentration driving force, the process is described herein as
dialysis. When transport is primarily convective as a result of
bulk flow across the membrane induced by a pressure driving force,
the process is ultrafiltration or hemofiltration depending on the
need for substitution solution as the membrane passes small solutes
but rejects macromolecules. The term "ultrafiltration" can also
refer to the fluid removal from blood during a dialysis or a
hemofiltration process. That is, ultrafiltration refers to the
process of passing fluid through a selective membrane, such as a
dialysis or hemofiltration membrane, in dialysis,
hemodiafiltration, or a filtration process.
[0101] A "valve" is a device capable of directing the flow of fluid
or gas by opening, closing or obstructing one or more pathways to
allow the fluid or gas to travel in a particular path. One or more
valves configured to accomplish a desired flow can be configured
into a "valve assembly."
[0102] The term "water reservoir" refers to an object that can be a
stand-alone enclosure or alternatively can be integrally formed
with an apparatus for hemodialysis, hemodiafiltration, or
hemofiltration. The object can store a source of water, and can be
configured to interface with at least one other functional module
found in systems for hemodialysis, hemodiafiltration, or
hemofiltration. For example, the water reservoir can contain at
least one fluid pathway and include components such as conduits,
valves, filters or fluid connection ports.
Sensing and Storage System
[0103] The sensing system of the first and second aspects of the
invention utilizes at least two flow sensors; inflow sensor 3 and
outflow sensor 4, control pump 7, and a dialysate flow path 1
having a controlled volume, as defined herein, as shown in FIG. 1.
The inflow sensor 3 and outflow sensor 4 can detect flow of
dialysate on either side of a dialyzer 35. Inflow sensor 3 can be
positioned in the dialysate flow path 1 after an optional infusate
reservoir 23, sodium chloride reservoir 15, or bicarbonate
reservoir 18, and therefore fluid can neither be added nor removed
from the dialysate loop 1 by any fluid pumps between inflow sensor
3 and outflow sensor 4, with the exception of fluid that passes to
or from the patient through a semi-permeable dialysis membrane (not
shown) of the dialyzer 35. The difference between the rates of
fluid flow at inflow sensor 3 and outflow sensor 4 is therefore
only due to net fluid changes due to movement of fluid from the
extracorporeal circuit 2 to the dialysate loop 1 and from the
dialysate loop 1 into a control reservoir 5. In any embodiment of
the first and second aspects of the invention, the control
reservoir 5 can be an ultrafiltrate reservoir, configured to
receive fluid removed by ultrafiltration.
[0104] Because net fluid flow between the extracorporeal circuit 2
and dialysate loop 1 having a controlled volume of the dialysis
system can be precisely determined by the difference in the rates
of flow between inflow sensor 3 and outflow sensor 4, accurate
control over fluid balance to the patient can be achieved using
only control pump 7, without the use of balance chambers, scales or
gravimetric control, and without coordination of the actions of
fluid pumps, such as infusate pump 24, water pump 11, and sodium
chloride pump 16. The pump rate of the control pump 7 only needs to
be adjusted based on the deviation of the prescribed fluid removal
session for a patient from the difference between the rates of
dialysate flow at inflow sensor 3 and at outflow sensor 4. In
general, adjusting the pump rate of a control pump 7 based on a
deviation generally refers to the process of changing the pump rate
of the control pump 7 in order to make the fluid removal rate
closer to the fluid removal rate set in a fluid removal
prescription.
[0105] A control system 47 may automatically adjust the pump rate
of control pump 7 by sending signal 50 to control pump 7, based on
the difference between the dialysate flow rate measured by the
inflow sensor 3, sent to the control system 47 by signal 48, and
dialysate flow rate measured by the outflow sensor 4, sent to the
control system 47 by signal 49, as compared to the prescribed rate
for a particular patient 44. Regardless of the volume of fluid
added from bicarbonate reservoir 18, sodium chloride reservoir 15
or infusate reservoir 23, the pump rate of the control pump 7 can
be adjusted to maintain the proper net fluid flow from the patient
44 to the control reservoir 5. The signals between the pumps, flow
sensors and the control system 47 may be sent wirelessly or through
wired communication.
[0106] Fluid removed from the patient during dialysis by
ultrafiltration can flow through fluid removal line 8 and control
reservoir connector 9 and into the control reservoir 5. In any
embodiment of the first and second aspects of the invention, the
control reservoir 5 may be large enough to accommodate all of the
fluid that needs to be removed during dialysis. In any embodiment
of the first and second aspects of the invention, the control
reservoir 5 can be smaller, and drain clamp 6 can be opened when
the control reservoir 5 is filled to allow draining from the
control reservoir 5 into a drain. In any embodiment of the first
and second aspects of the invention, connector 9 being in fluid
communication with control reservoir 5 is not required. Instead,
fluid removal line 8 can directly connect to a drain (not shown).
In other embodiments, the fluid removal line 8 can serve as a
conduit to introduce fluid rather than remove fluid back into a
fluid pathway or fluid line as required. For example, the fluid
removal line 8 can serve to facilitate movement of fluid during a
blood rinse back operation or cleaning cycle away from a control
reservoir 5 and back into the dialysate flow path 1 where a
suitable fluid can be provided. For example, a cleaned dialysate
fluid blood, or any other suitable fluid can be retuned back to a
patient as a fluid bolus at an end of a treatment via the fluid
removal line 8 During treatment, fluid may be added from sodium
chloride reservoir 15 in order to control the sodium chloride
concentration of the dialysate; from bicarbonate reservoir 18 in
order to control the bicarbonate concentration of the dialysate;
and from cation infusate reservoir 23 in order to control the
concentration of other cations in the dialysate, such as calcium,
potassium or magnesium. The control reservoir 5, therefore, can be
large enough to hold the sum of these volumes. In any embodiment of
the first and second aspects of the invention, the control
reservoir 5 can have a fluid capacity of about 15 L, which is
generally enough to contain all necessary fluids for a normal
dialysis session. In any embodiment of the first and second aspects
of the invention, the control reservoir 5 may be larger or smaller.
In any embodiment of the first or second aspects of the invention,
the control reservoir 5 can be between any of 1 L-30 L, 1-3 L, 1-5
L, 3-10 L, 8-15 L, 12-20 L, 15-18 L or 18-30 L. Clamp 6 can control
drainage from the control reservoir 5. In any embodiment of the
first and second aspects of the invention where the control
reservoir 5 is not large enough to hold all of the necessary
volume, the control reservoir 5 can be fluidly connected to a drain
(not shown) and clamp 6 can be opened during treatment to drain the
control reservoir 5 and allow for additional fluid removal.
[0107] The pumps utilized by the fluid balancing system of the
first and second aspects of the invention can be any type known in
the art, including but not limited to, gear pumps, peristaltic
pumps, diaphragm pumps, and impeller pumps. Because the patient
fluid removal rate can be precisely controlled by the control pump
7 utilizing the inflow sensor 3 and outflow sensor 4, the fluid
pumps used to add water, sodium chloride, infusates and bicarbonate
need not be absolutely precise. If more fluid than is necessary is
added by any one of these pumps, the control system 47 can
automatically detect a change in the difference between flow
measured at inflow sensor 3 and outflow sensor 4 and adjust the
pump rate of control pump 7 automatically.
[0108] In any embodiment of the first and second aspects of the
invention, control pump 7 may be operated bi-directionally. That
is, control pump 7 may be operated in the influx direction in order
to move fluid from the control reservoir 5 to the dialysate flow
loop 1; or control pump 7 may be operated in the efflux direction
in order to move fluid from the dialysate flow loop 1 into the
control reservoir 5. When the control pump 7 is operated in the
influx direction to move fluid from the control reservoir 5 to the
dialysate flow loop 1, check valve 37 ensures that the fluid volume
introduced to the dialysate flow path 1 from control reservoir 5
must first pass through sorbent cartridge 27 before passing into
the dialyzer.
[0109] Blood is circulated from the patient 44 to the dialyzer 35
through the extracorporeal circuit 2 by blood pump 45. Blood
pressure monitor 46 can be used to monitor the blood pressure of
the patient 44 before, during or after treatment. The measured
blood pressure can correspond to the rate of removal of fluid from
the patient. If fluid is removed from the patient 44 at too high of
a rate, the patient's blood pressure can drop to dangerous levels.
In any embodiment of the first and second aspects of the invention,
the pump rate of control pump 7 can automatically be adjusted due
to changes in patient blood pressure detected by blood pressure
monitor 46. If the blood pressure detected by blood pressure
monitor 46 is too low, the pump rate of control pump 7 can
automatically be reduced. In any embodiment of the first and second
aspects of the invention, the pump rate of control pump 7 can be
increased if the measured blood pressure does not show a
significant drop.
[0110] The dialysis system shown in FIG. 1 is a controlled volume
dialysis system. This means that net passive movement of fluid
volume across the dialysis membrane (not shown) due to operational
pressure changes can be eliminated. The system shown in FIG. 1 does
not contain any open or flexible reservoirs, and therefore the
volume of fluid recirculating through the dialysate flow path is
substantially fixed. In any embodiment of the first and second
aspects of the invention, the dialysis system or dialysate flow
loop can be controlled compliant. In any embodiment of the first or
second aspects of the invention, the user can make the system
operate as a controlled compliant dialysis system by ensuring that
all reservoirs or drains are closed or have a substantially
inflexible volume. Because there is no net passive movement of
fluid volume across the dialysis membrane, the net movement of
fluid across the dialysis membrane is controlled by the operational
pumps of the system. In any embodiment of the first and second
aspects of the invention, removal of fluid from the dialysate flow
path 1 can result in a vacuum being created in the dialysate flow
path 1, due to the fact that the dialysate flow path 1 has a
substantially inflexible volume. In the event of factors that tend
to increase pressure on the extracorporeal side of the dialysis
membrane, such as increased blood flow rate or blood viscosity,
pressure across the membrane will automatically be equalized due to
the limited volume of the dialysate flow path and the
non-compressible nature of the dialysate. In the event of factors
that tend to increase pressure on the dialysate side of the
dialysis membrane, such as increased dialysate flow rate, net
movement of water from the controlled volume dialysate flow path to
the extracorporeal flow path is prevented by a vacuum that would
form in the controlled volume flow path in the event of such a
movement, due to the fixed volume of the controlled volume flow
path.
[0111] Other sorbent-based regenerative hemodialysis systems known
in the art have dialysate solution reservoirs that are located in
the dialysate flow path between the dialyzer outlet 34 and the
dialyzer inlet 33. In these known systems the dialysate reservoirs
are in some cases open reservoirs and in other cases they are
flexible volumes such as bags. One skilled in the art will
understand that, in such systems, the inclusion of such reservoirs
in between the dialyzer outlet 34 and the dialyzer inlet 33
inhibits precise control of patient net fluid volume removal by
means of inflow sensor 3, outflow sensor 4, and control pump 7
because dialysate flow path 1 will no longer have the
characteristic of a controlled volume dialysate flow path. Thus,
the application of inflow sensor 3, outflow sensor 4 and control
pump 7 to control net patient fluid volume removal within the
context of a controlled volume flow path is a critical feature of
the present invention.
[0112] During dialysis, blood will be circulated from the patient
44, through an extracorporeal circuit 2, to dialyzer 35, and back
to the patient 44. Dialysate will be circulated in a dialysate flow
path 1 on the opposite side of the dialyzer 35 from the patient's
blood. Blood contacts a semi-permeable membrane (not shown) in the
dialyzer 35 that separates the extracorporeal circuit 2 from the
dialysate circuit 1. Waste species in the patient's blood can cross
the semi-permeable membrane and enter the dialysate.
[0113] Fluid movement through the dialysate circuit 1 of the first
and second aspects of the invention is controlled by dialysate pump
43. Dialysate enters the dialyzer 35 through dialyzer inlet
connector 33 and leaves through dialyzer outlet connector 34. The
spent dialysate can travel past outlet filter 36. Check valve 37
serves to ensure that any fluid added to the system cannot travel
past dialyzer connector 34 and into the dialyzer 35, but instead
must travel through the circuit and sorbent cartridge 27 to reach
dialyzer 35. The control pump 7 through connector 9 and water pump
11 through connector 12 can be used to draw water out of the
dialysate circuit 1, and thereby cause a net removal of fluid from
the patient, or add water to the dialysate circuit 1. Fluid removed
from the patient can pass through fluid removal line connector 9
and into the control reservoir 5.
[0114] Water reservoir 10 can be used to add fluid to the dialysate
circuit as needed. Water reservoir pump 11 can draw water out of
the water reservoir 10, through water reservoir connector 12 and
past water filter 13. Vent 14 allows the pressure to be equalized
as water is removed from the water reservoir 10. The spent
dialysate then travels into sorbent cartridge 27 where the toxins
are removed from the spent dialysate. The spent dialysate enters
the sorbent cartridge 27 through sorbent cartridge inlet connector
29, and leaves through sorbent cartridge outlet connector 28.
Sorbent cartridge check valve 30 ensures that fluid cannot enter
the sorbent cartridge 27 in the opposite direction, or leak from
the dialysate flow path when sorbent cartridge 27 is disconnected
at connector 28.
[0115] Sodium chloride, bicarbonate, and other cation infusates may
be added to the dialysate. Sodium chloride pump 16 can draw
dialysate into the sodium chloride reservoir 15 or bicarbonate
reservoir 18, through bicarbonate reservoir connectors 19 and 20.
Diverter valve 21 can control the addition of sodium chloride or
bicarbonate from the reservoirs into the dialysate. Sodium chloride
check valve 17 ensures that fluid cannot pass through the sodium
chloride reservoir 15 in the opposite direction. Fluid from the
sodium chloride reservoir 15 and bicarbonate reservoir 18 can enter
the dialysate flow loop through connector 22. Cation infusate pump
24 can control the addition of infusate from cation infusate
reservoir 23 into the dialysate through cation infusate reservoir
connector 26. Vent 25 in cation infusate source 23 can allow the
equalization of pressure during addition of the infusate.
[0116] In any embodiment of the first and second aspects of the
invention, a small amount of dialysate can be drawn off by chemical
sensor valve 42 to detect the levels of chemicals in the dialysate
before returning to the dialyzer 35. By opening sensor valve 42,
fluid can be drawn through sensor line 38 and to ammonia sensor 39,
pH sensor 40, and carbon dioxide sensor 41. If the levels of
chemicals in the dialysate are outside of the proper
concentrations, the appropriate infusates can be added to the
dialysate as described above, or dialyzer bypass valve 31 can be
activated to prevent the dialysate from reaching dialyzer inlet
port 33. In any embodiment of the first and second aspects of the
invention, chemical sensors 39, 40 and 41 can optionally be located
in the main dialysate flow path and a separate sensor line 38 is
not required.
[0117] The spent dialysate then passes by dialyzer bypass valve 31,
which can cause the dialysate to bypass the dialyzer 35 if
necessary through dialyzer bypass line 32. In normal operation,
dialyzer bypass valve 31 will be set to allow dialysate through
dialyzer 35. The dialysate then passes through dialyzer inlet
connector 33, and back into the dialyzer 35.
[0118] Failure to precisely control patient net fluid removal can
be hazardous to the patient. Inadequate fluid removal can lead to
blood pressure derangements and pulmonary edema. Excessive removal
can lead to lead to a dangerous drop in blood pressure. For this
reason, independent protective systems that can detect a failure in
the ultrafiltration control system and act to prevent patient harm
due to net fluid removal errors are beneficial. The ultrafiltration
control system of the dialysate flow path of the first and second
aspects of the invention shown in FIG. 1 can be periodically
self-tested by temporarily stopping pumps 7, 11, 24, and 16 to stop
all dialysate flow path 1 fluid ingress and egress to make the
ultrafiltration rate equal to zero, and then comparing the readings
at inflow sensor 3 to outflow sensor 4. If the flow sensors
providing measurements to the control system are operating
properly, the reading at inflow sensor 3 will be identical to the
reading from outflow sensor 4 within predetermined error limits. If
the error between inflow sensor 3 and outflow sensor 4 is outside
of predetermined limits, then the dialysis process can be stopped
before the patient is harmed. Further, those of skill in the art
will understand that the protective system described will not be
possible with systems known in the art that have an open or
flexible reservoir in the main dialysate flow path 1 between the
dialyzer outlet 34 and dialyzer inlet 33.
[0119] In any embodiment of the first and second aspects of the
invention, redundant flow sensors can be added as part of an
independent protective system. For example, one or more additional
redundant outflow sensors can be placed between the dialyzer 35 and
the first fluid pump after the dialyzer 35. The additional outflow
sensor can be used to determine whether the primary outflow sensor
4 is properly functioning. If the additional, redundant outflow
sensor detects a flow that is different from outflow sensor 4, the
difference may show that outflow sensor 4 is not working properly.
In response, dialysis can be stopped until a determination of which
sensors are not working properly can be made. Similarly, one or
more redundant inflow sensors can be included between the dialyzer
35 and the first fluid pump in the flow loop prior to the dialyzer
35. As with the redundant outflow sensors, redundant inflow sensors
can provide an independent protective system by ensuring that
inflow sensor 3 is properly functioning.
[0120] The flow path of the first and second aspects of the
invention described in FIG. 1 can also control patient net fluid
volume when a bolus of fluid is delivered from the dialysate flow
path 1 to the extracorporeal circuit 2 and to the patient 44. To
deliver a precise bolus of fluid to the patient, the pumping rate
of control pump 7 in the efflux direction can be reduced, stopped
or, in any embodiment of the first and second aspects of the
invention, reversed to provide influx flow to dialysate flow path
1. If the incoming fluid volume provided by the other metering
pumps, such as cation infusate pump 24 and water infusion pump 11
is not sufficient to provide the desired patient fluid bolus, the
rate of one or more of the pumps, such as water infusion pump 11
can be increased to provide a precisely controlled fluid bolus
volume to the patient at the desired rate. If the addition of water
by means of pump 11 causes the concentrations of sodium or
bicarbonate to become less than desired, pump 16 can be operated to
infuse sodium chloride and/or sodium bicarbonate to achieve the
desired concentrations. This functionality beneficially allows the
a fluid bolus to be provided to the patient without requiring the
expense of a bag of saline or the time required to connect the
saline bag to the flow path. The reduced time required to initiate
delivery of the fluid bolus to the patient is especially beneficial
when rapid intervention is required to correct a severe hypotensive
episode in the patient. In general, transferring a volume of fluid
from a dialysate flow path to an extracorporeal flow path will be
understood to refer to a process of adding fluid to a dialysate
flow path such that fluid is transferred across a dialyzer into an
extracorporeal flow path. One skilled in the art will understand
that the described functionalities are not possible with known
systems having open or flexible reservoirs in the flow path, nor
with other known systems, for example systems with volumetric
balance chambers.
[0121] The blood in the extracorporeal circuit 2 is normally
returned to the patient 44 at the end of a hemodialysis treatment.
Commonly, the fluid used to return the blood from the
extracorporeal circuit 2 is provided by means of a saline bag
connected to a port on the extracorporeal circuit 2. One skilled in
the art will understand that the fluid bolus volume control
function described herein can also be employed to provide
physiologically compatible fluid to the extracorporeal circuit 2 to
assist in returning the blood at the end of a hemodialysis
treatment. This functionality beneficially allows the blood to be
returned to the patient 44 without requiring the expense of a bag
of saline or the time required to connect the saline bag to the
flow path. One skilled in the art will understand that this
functionality is not possible with known systems having open or
flexible reservoirs in the flow path, nor with other known systems,
for example systems with volumetric balance chambers.
[0122] FIG. 2 is a flow diagram showing the operation of the system
of the first and second aspects of the invention. Initially, a
fluid removal prescription will be set for the patient 51. This is
the amount of fluid that needs to be removed from the patient and
the rate at which fluid will be removed from the patient. The pump
rate of the control pump will be set to remove the necessary amount
of fluid at the set rate 52. A control system can monitor the flow
rates of the dialysate at the inflow sensor and the outflow sensor
53. The difference in the flow rates at the inflow sensor and
outflow sensor is only due to the net fluid movement from the
dialysate flow loop to the blood flow loop and the removal of fluid
to by the control pump. If the rate of fluid movement from the
extracorporeal flow loop to the dialysate flow loop is not equal to
the fluid removal prescription, the pump rate of the control pump
can be altered, as shown by arrow 55. During the treatment, data
can be sent to the control system concerning the blood pressure of
the patient and the concentrations of chemicals in the dialysate
56. If necessary, fluid can be added from a sodium chloride
reservoir, sodium bicarbonate reservoir, fluid reservoir or water
reservoir to the dialysate flow loop 57, as explained above. The
addition of fluid to the dialysate flow loop can affect the net
movement of fluid from the extracorporeal flow loop to the
dialysate flow loop. This effect can be determined by monitoring
the difference in flow rates at the inflow sensor and outflow
sensor 53, and so the addition of fluid to the dialysate flow loop
does not affect the calculation of the net movement of fluid from
the dialysate flow loop to the blood flow loop 54.
[0123] The inflow sensor and outflow sensor of the present
invention can be any type of flow sensor known in the art that can
detect the flow of a fluid at a specific point. One non-limiting
example of a flow sensor is the commercially available 8000 Series
Liquid Flow Meter from Proteus Industries, Inc. In any embodiment
of the first and second aspects of the invention, the flow sensor
can be a turbine type flow sensor having an optical encoder to
allow the flow rate to be measured. However, any commercially
available or non-commercially available sensor that can accurately
measure the flow of a fluid is contemplated by this invention.
[0124] One skilled in the art will understand that various
combinations and/or modifications and variations can be made in the
dialysis system depending upon the specific needs for operation.
Moreover features illustrated or described as being part of an
aspect of the invention can be included in the aspect of the
invention, either alone or in combination.
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